MM API: V4L2_EVENT_RESOLUTION_CHANGE event never received

Autonomous Machines Jetson & Embedded Systems Jetson TX2
#1

I’m using the Multimedia API on JetPack 4.2.2 and try to setup the NvVideoDecoder.
As I understood, the NvVideoDecoder can only be used (setup capture plane) after the application has dequed an V4L2_EVENT_RESOLUTION_CHANGE event. However, I never receive this event in my custom application. I studied the samples code (00_video_decode and 14_multivideo_decode) and copied the code into my own application.

  1. Create NvVideoDecoder in non-blocking mode
  2. Subscribe to V4L2_EVENT_RESOLUTION_CHANGE event
  3. Create and start device poll thread (why do I need an own thread for this?)
  4. In the main loop I call SetPollInterrupt, wait on the semaphores, and dqEvent:

    dec->SetPollInterrupt();
    decoderPollCtx.pollthread_sema);
    sem_wait(&decoderPollCtx.decoderthread_sema);
    v4l2_event ev = {};
    int ret = dec->dqEvent(ev, 100);
    if (ret == 0 && ev.type == V4L2_EVENT_RESOLUTION_CHANGE)
    {
    query_and_set_capture(&decCtx);
    }

The event is never dequed and query_and_set_capture is never called, even after several minutes and hundreds of loop iterations.
What exactly has to be done to cause the kernel to emit a V4L2_EVENT_RESOLUTION_CHANGE event?

The 00_video_decode sample interestingly works, but only the version that was installed via the SDK in /usr/src. If I download the samples as part of the Multimedia-API package (L4T 32) from the download site and build them, it can’t decode and play the sample video.

#3

Hi,
The samples have to fit release version. We suggest you install jetson_multimedia_api packages through SDKManager and build your application by referring to header files in

/usr/src/jetson_multimedia_api/include